Endothelial apoptosis is induced by serum of patients after cardiopulmonary bypass

Objective: Increased serum levels of a multitude of mediators like interleu kins, tumor necrosis factor, elastase, adhesion molecules, and endotoxin ha ve been described following cardiopulmonary bypass (CPB). The biological co nsequences of this complex response are unclear. Methods: Serum samples of nine patients scheduled for elective coronary artery bypass grafting were o btained preoperatively and 1, 6, and 12 h after weaning from CPB. Additiona l serum samples were obtained perioperatively from four patients undergoing major lung resection and from four healthy volunteers. The apoptosis-induc ing activity of serum samples on endothelial cells was examined using a tis sue culture assay system. Endothelial cells were derived from human umbilic al cords and incubated for 48 h with serum samples in various dilutions dur ing their second passage. The culture plates were fixed with methanol/aceto ne and stained with the DNA dye diamidinophenylindole. Apoptotic and normal cells were identified and counted using phase contrast and fluorescence mi croscopy. Results: The proportion of apoptotic endothelial cells was 5.6-fo ld higher in culture plates incubated with diluted (30%) serum samples obta ined at 6 h after weaning from CPB when compared to plates incubated with p reoperative samples (P = 0.0077). A smaller effect occurred already at 1 h in some patients, whereas at 12 h after weaning from CPB no increased endot helial apoptosis was observed. No proapoptotic activity was found in preope rative as well as in control samples from patients undergoing lung resectio n or from healthy volunteers. Conclusions: Serum of patients after CPB exer ts a strong apoptosis inducing activity on human endothelial cells. Apoptot ic death of endothelial cells following CPB may be responsible for postoper ative vascular and bypass dysfunction including phenomena like increased ca pillary permeability. (C) 2000 Elsevier Science B.V. All rights reserved.